The present invention relates to an apparatus for discriminating cylinders of an internal combustion engine on the basis of the signal from a single system of a rotary signal generator for detecting the rotary angle of the internal combustion engine having plural cylinders.
Conventionally, as such a kind of a cylinder discriminating apparatus, a technique as disclosed in e.g. Unexamined Japanese Patent Publication Hei-3-121238 has been known.
In response to the square wave signal from a single system of a rotary signal generator, the cylinder discriminating apparatus discriminates cylinders on the basis of the ratio of the duration of its H level to one period of the square wave signal.
Such a cylinder discriminating method is established only when the revolution of the internal combustion engine is stable, but may erroneously discriminate the cylinders when it is unstable. This is because the square wave signal alters when the number of revolutions is unstable. Hence, errors are included in the ratio of the duration of its H level to the one period of the square wave signal.
In order to obviate such an inconvenience, since the cylinders may be erroneously discriminated at the starting time when the revolution is not stable, the technique disclosed in the above reference inhibits discriminating cylinders during a predetermined time.
However, the conventional cylinder discriminating device has bare possibility of erroneously discriminating cylinders at the starting time, but cannot prevent cylinders from being erroneously discriminated in an operation when rotational fluctuation occurs in a running state after starting, such as incomplete clutching operation.